Seasonal to Interannual Storm Controls on Coastal Morphology at
NASA-Kennedy Space Center
Abstract
Large storms are considered to be influential drivers of morphologic
change on open sandy coasts. Whereas storm-driven morphologic changes
and the recovery processes that typically follow have been robustly
documented, less well understood is the concept of storm-driven coastal
behavior over seasonal to annual timescales, which integrates multiple
storm response and recovery cycles. In this study, storm controls on
coastal evolution are evaluated using a topographic dataset containing
monthly measurements of the intertidal and subaerial beach for 5 years
(2009-2014) along a 10 km reach of open sandy coast fronting
NASA-Kennedy Space Center near Cape Canaveral, Florida. In addition to
shoreline and volume change analyses, a novel Empirical Orthogonal
Function (EOF) analysis has been applied to these data to extract
dominant spatial and temporal patterns of morphologic change over the
full beach surface, as opposed to being applied over individual
cross-shore transects or alongshore contours as previously practiced.
Results indicate that the most dominant pattern of morphologic evolution
within these data describes an isolated change of state to this system
initiated by the impact of Hurricane Sandy (2012). This is exhibited
physically as a southward migration of a previously stable cuspate
foreland beginning immediately after the storm, resulting in nearly 600
m of propagation over the following 1.5 yr observation interval.
Additionally, remaining dominant patterns describe a seasonal erosion
cycle linked to storm driven seasonality in nearshore water levels, and
a spatially variable berm formation cycle on inter-storm timescales
likely driven by storm-induced variations in sediment storage locations
and associated availability to non-storm hydrodynamics. These results
illustrate that coastal response to an individual storm may control the
recovery processes that follow by shifting morphologic equilibria such
that processes of recovery drive the beach toward a configuration unlike
its pre-storm state. Because these post- event processes influence
morphologic response to the next event, the results presented here
highlight a largely unexplored coupling between storm response and
recovery that may be considered a dominant control on interannual-scale
coastal evolution in storm-prone regions.